Aerial pesticide spray may be the next step in South Florida’s fight against the Oriental fruit fly, Florida Commissioner of Agriculture Adam Putnam told a crowd of nearly 100 farmers Monday in Homestead.

Still at question is when to spray.

Many of the growers Monday, whose tomatoes, avocados, strawberries and other crops are threatened by the invasive fruit fly, questioned why spraying will not begin immediately.

If scientists find a pregnant female, find larvae or see the numbers of flies in traps rise, Putnam said the state will likely begin aerially spraying GF-120, an insecticide approved for organic farming, which he called the “last, best bullet in the gun.” But angry growers, concerned about their livelihoods, grilled the commissioner. They want spraying done before the fly spreads any farther than the 85-mile quarantine in Redland, Florida.

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Dr. Trevor Smith, division director of plant industry at the Florida Department of Agriculture, told the crowd that aerial spraying wouldn’t eradicate larvae already in crops, so scientists are sticking with the current pheremone and insecticide-laced traps for now.

Putnam said he sent a team to Washington, D.C. to negotiate with the Environmental Protection Agency for clearance to use the pesticide Malathion for hand-spraying crops before harvest. Malathion was aerially sprayed to fight Mediterranean fruit flies in outbreaks in California in 1989 and Hillsborough County in 1997.

In large doses, Malathion can cause nausea, dizziness and confusion, but the EPA has approved the pesticide for aerial spraying over residential areas for insect control.

“They will cut and paste the protocol they have for Malathion in California and give it to us,” Putnam said.

But, he noted, the California protocol doesn’t include every crop grown in South Florida. Putnam said those exceptions are being negotiated and could be approved “as early as next week.”

Organic farmers at the meeting expressed concerns about the spraying of Malathion, which would invalidate their organic status and put them out of business for at least three years, according to one grower.

What Putnam called “by far the largest outbreak we’ve had in this state’s history,” could seriously impact the $1.6 billion agriculture industry in Miami-Dade County.

Scientists found one fruit fly since the state of agricultural emergency went into effect Sept. 15, bringing the total count to 159 flies in the South Florida outbreak.

Growers have signed compliance agreements, which signal their willingness to aid the state eradication effort. This includes spraying their crops with insecticide every six to 10 days and potentially destroying infected crops. More than 8 tons of fruits and vegetables have been destroyed so far as a result of the South Florida outbreak.

“We have zero flexibility to help if we don’t have that compliance agreement in place,” Putnam told the crowd.

Joe DeSousa, a farmer with land in the affected area, asked Putnam if there was any compensation planned for the farmers who lose their livelihoods in the eradication effort.

“Not so much for profit,” DeSousa said. “But for investment in the next round, we plant. We’re dying down here.”

Putnam acknowledged there was nothing in place but didn’t rule out future compensation.

Paul Hornby, state plant health director for the U.S. Department of Agriculture’s plant protection and quarantine, said Florida has had 75 fruit fly incursions since 1999, leaving his team well versed in the procedures.

“We are good at this,” he said. “We have decades worth of science, research and experience.”

Other methods of attack include post-harvest irradiation. So far, only a single shipment of possibly infected dragonfruit was sent to Mississippi for irradiation.

Putnam mentioned he was negotiating with Food Technology Service Inc, a medical irradiation plant in Mulberry, Florida, to take on crop irradiation if need be.

If no additional flies are found, the quarantine is set to end Jan 18.

“I hope we’re not dealing with this a year from now, but we will be dealing with this 120 days from now,” Putnam said.

An earlier version of this story incorrectly reported that Malalthion would be used in aerial spraying. State officials are seeking permission to use Malathion only for hand-spraying.